•The combined steam and dry reforming of methane was carried out over a catalytic nickel membrane.•The reaction was carried out over a very short residence time of 120 ms (GHSV = 30,000 h−1).•H2/CO ratio could be adjusted by varying the CO2/H2O ratio in the feed stream for the GTL process.•No carbon formation on the catalytic nickel membrane was observed.

In this study, test on the combined steam and dry reforming of methane were carried out over a catalytic nickel membrane within a very short residence time of 120 ms under different process conditions (CO2/H2O feed ratio and temperature). The effect of the molar ratio of CO2/H2O in the reactants on the H2/CO ratio in the products was investigated at 923–1023 K. In the reaction of the combined steam and dry reforming of methane, CH4 conversion was strongly influenced by the CO2/H2O feed ratio and decreased with the increase in the CO2/H2O feed ratio at 923 K, while the influence of the CO2/H2O feed ratio on CH4 conversion was not significant at temperatures ≥973 K. Unlikely CH4 conversion, the conversion of CO2 increased with the increase in the CO2/H2O feed ratio over the temperature range of 923–1023 K. The conversion of CH4 and that of CO2 both increased with increasing temperature because the corresponding reactions are endothermic and remained nearly constant at temperatures ≥973 K. The H2/CO molar ratio could be adjusted by the CO2/H2O feed ratio for downstream applications. No carbon deposition on the catalytic nickel membrane was observed after the combined steam and dry reforming of methane tests under all process conditions.